Expansion joint systems of various types are well known in the prior art. Expansion joint systems are used to bridge a slot that extends between adjacent slabs of concrete or other rigid materials which make up the traffic surfaces of a roadway, bridge, parking deck or plaza deck. The slabs are relatively movable to one another due to factors such as loading, thermal expansion and contraction, and settling. The slot enables the slabs to move relative to one another without damaging the structural integrity of either slab.
Expansion joint systems are used to bridge the slot between the adjacent slabs, and to maintain the continuity of the traffic surface in the area over the slot. Expansion joint systems must function despite cyclical increases and decreases in the width of the slot, and changes in vertical elevations of the slabs. The expansion joint must also prevent contaminants such as water, road salt and dirt from infiltrating the slot. The infiltration of such contaminants may result in damage to the slabs or to the supporting structure underlying the slabs.
A well known prior art expansion joint system has included a vertically recessed boxed out area in the slabs adjacent the slot. A plate member is positioned in the boxed out area and spans the slot. A pad of resilient material is positioned above the plate member. The pad typically has an upper surface that is at the level of the traffic surfaces of the adjacent slabs. The pad is usually rectangular in cross section, and is either preformed or molded in place depending on the type of joint system.
Nosings typically extend on either side of the pad. The nosings are formed in place and are comprised of a resilient material that is somewhat harder than the pad. The nosings serve to bond the pad to the walls of the slabs in the boxed out area. The nosings are also typically filled to the vertical height of the traffic surfaces of the slabs.
As the slabs move relative to one another, the plate member of the expansion joint system slides on the horizontal surfaces of the slabs in the boxed out area. The resilient pad and nosings expand and contract as the slabs move relative to one another.
It is not uncommon for adjacent slabs to move apart more than anticipated by the designer of the structure. In such circumstances the pad will usually separate from one of the nosings along a vertical side wall of the rectangular slab. When this occurs the integrity of the joint system is lost. Water and other contaminants infiltrate the slot and may cause damage. In cold climates, water which has infiltrated the slot will undergo freeze and thaw cycles which is particularly damaging to the adjacent slabs.
Unfortunately, failures of expansion joint systems are particularly common in cold conditions. This is because the pad and the nosings often become very brittle as temperature decreases. Impacts on the expansion joint due to heavy traffic or movement of the slabs due to loading or contraction, may cause the nosings and the pad to separate.
Problems may also arise when the expansion joint system must be installed in cold weather. In such conditions the materials commonly used to form the nosings cannot cure as well as in warmer weather. This may result in a poor bond between the pad and the nosings which causes premature separation at a bond line between the pad and the nosings.
Thus, there exists a need for an expansion joint system that achieves greater elongation and greater failure resistance, particularly in cold temperatures.